On many occasions, timepieces have been presented equipped with an antenna and a micro receiver in order to capture radio diffused signals. If such timepiece is in the form of a wristwatch, the antenna is generally located within the bracelet as is the case in arrangements described for instance in the patent documents Nos. FR-A-1 207 640, EP-A-0 100 639, EP-A-0 125 930, EP-A-0 184 606 and WO-A-86/03645. But locating the antenna within the bracelet of a watch gives rise to problems of providing connections between the input to the receiver located in the watchcase and the antenna which forms a part of the bracelet, this latter a movable element, generally hinged on the case by means of lugs. The leadthrough of the antenna conductor thus gives rise to constructional problems which require solutions not always simple. At the leadthrough for instance the conductors are mechanically stressed and they break off more or less rapidly if means are not provided to avoid such breakage. The means are demanding and complicate changing the bracelet, a bracelet moreover which must be specially built since it carries an antenna and which may not always be exchanged with a bracelet readily found on the market.
To incorporate a micro receiver with its antenna within a case worn by a person, is known from relatively recent developments. There is for instance a receiver developed by the Motorola company and confined to a case in the form of a pen provided with a clip which serves to attach the pen to a portion of the clothing. Such a product has been made known under the registered trademark "Sensar". There is likewise known a receiver from the Philips company which takes the form of an elongated parallelepipedon likewise provided with a clip enabling it to be attached to an article of clothing. This receiver is known as the "Pager 32 B" and its approximate dimensions are 10 cm in length and 2 cm in width and thickness.
The receivers just mentioned have dimensions sufficiently great so that incorporation of an antenna does not pose very grave problems. However, it seems admissible that to incorporate an antenna into the case of a timepiece capable of being worn on a portion of the body, for example a wristwatch or a pendant watch, poses problems far more difficult to solve in view of the very limited space which is available for mounting such antenna.
Efforts have however been made in order to resolve this problem. Thus, the French patent document No. FR-A-2 505 105 (U.S. Pat. No. 4,419,770) describes a wrist AM radio receiver including a PLL synthesizer as local oscillator. This receiver, provided with an electronic watch, is equipped with an antenna in the form of bar mounted in the watchcase, such case being rounded in order to hug the curve of the wrist. The figures accompanying the document show clearly that the bar is directed in the sense of the width of the bracelet, this making the antenna sensitive to the component of the magnetic field situated longitudinally to the cylinder which forms the wrist. This arrangement is unfavourable as will appear in the description of the invention to follow.
The English abstract of the patent document No. JP-A-52-48 364 appearing in "Patent Abstracts of Japan", vol. 1, Nr. 116, Oct. 4, 1977, page 4486 E77, describes a timepiece under the glass of which is placed a single line antenna. It has been however determined that such an antenna is inefficient in the range of frequencies considered hereinafter, if it is not associated with another conducting element in order to form a capacitive antenna sensitive to the component of the electrical field located radially to the cylinder which forms the wrist.